A large number of shower baths are installed every year. A typical shower employs a floor drain that is located near the middle of the shower floor which is inclined downwardly toward the drain. For floors made of stones such as marble or granite, the stones must include additional diagonal cuts to create the slopes of incline toward the drain, requiring additional labor time and resulting in an aesthetically unpleasing look. The required cuts also limit the patterns that can be created by setting the stones. The additional cuts also trap dirt and mildew. Moreover, a metallic drain cover is placed over the drain and serves as a strainer. Strong acidic cleaning agents used to clean the stones react with the metal in the drain cover discolor the metallic drain cover, further worsening the appearance of the shower floor. For many years, these problems which are unique to stone shower baths have persisted without a satisfactory solution. Because stones are selected for their aesthetic appeal, the problems of appearance are of great significance.